She said the 54-member bloc -- which is headquartered in Addis Ababa -- would boost efforts "towards the restoration of effective state institutions and security in Libya."

The United States has called the killings "brutal mass murder", while the European Union said it was a "criminal" effort to create religious divisions.

Almost two-thirds of Ethiopians are Christians, the majority of those Orthodox Copts -- who say they have been in the Horn of Africa nation since the first century AD -- as well as large numbers of Protestants.

Islam also has an ancient history in Ethiopia, brought to the country by some of the earliest followers of the Prophet Mohammed (PBUH), who were sheltered there by the Christian king.

Awash with weapons since its 2011 revolt and torn between rival governments and parliaments, Libya is on the edge of all-out civil war as armed groups do battle for its cities and oil wealth.

The Islamic State, which has seized chunks of Syria and Iraq, has won the support of jihadist groups across Middle East and north Africa. Several Libyan jihadist groups have pledged allegiance to the militants.